i've read that oscars can and do have a tendency to rearrange their tanks decor and such, so i think they would uproot any plants you might have in there. give it a shot, if you don't mind having it possibly not work, but it is worth the try, as plants can be a very beneficial part of keeping a tank's water healthy. i have no experience with oscars and planted tanks myself, so i don't know if your fish would eat the plants. and this might depend some on the particular oscar's appetite for greenery too.
maybe you might try a potted sword or two, and use those reddish brown clay pots and pile the tank's substrate about halfway up the pot side to keep it from tipping or getting knocked over. how big is your oscar? if he's still little, you can more wood/stones/etc, since he's not full size and probably can't knock down a lot of stuff.